Method and system for delivering a self-expanding stent to the venous sinuses

ABSTRACT

A stent delivery system includes a shaft extending from a proximal end of the system into a delivery tip at a distal end. The shaft includes a coil and a stent bed. A stent is loaded onto the stent bed and has a first portion at its distal end having a greater flexibility than a second portion at its proximal end. Sheathing is moveable over the stent bed between pre-deployed and deployed positions. The sheathing includes a flexible section at the sheathing distal end, a semi-flexible section adjacent the flexible section, and a stiff section adjacent the semi-flexible section. The delivery tip is more flexible than the combination of the stent bed, the first portion of the stent, and the flexible section of the sheathing, which is more flexible than the combination of the stent bed, the second portion the stent, and the flexible section of the sheathing.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

[Not Applicable]

FIELD

Certain embodiments relate to stents and systems and methods fordelivering a stent. More specifically, certain embodiments relate to amethod and system for treating a stenosis or collapse in the venoussinuses by delivering a self-expanding stent. In various embodiments,the self-expanding stent comprises a proximal end having a first radialoutward expansion strength (RES) that is greater than a second RES at adistal end of the stent. In a representative embodiment, the proximalend of the stent comprises a diameter that is greater than the diameterat the distal end of the stent. In certain embodiments, the flexibilityof the stent delivery system and/or the stent increases from theproximal end toward the distal end of the system and/or stent.

BACKGROUND

When blood exiting the brain is slowed by a restriction in the venoussinuses, it causes an increase to the distal blood pressure, which maytranslate to an increase in the brain fluid pressure. Patientsexperiencing Increased Intracranial Pressure (ICP), where the CerebralSpinal Fluid (CSF) pressure in the cranium has increased, may sufferfrom headaches, loss of vision, and/or tinnitus, among other things. Thepreferred method for treating a collapse of and/or a stenosis in thesigmoid and/or transverse sinus has been drugs and/or using a shunt torelieve the CSF fluid pressure. The use of drugs or a shunt is notideal, however, because both are temporary solutions that each carryassociated risks.

More, recently, a new procedure has been carried out that involvesplacing a stent in the venous sinus system of patients to ameliorate acollapse of and/or a stenosis in the sigmoid and/or transverse sinus andto restore improved blood flow out of the brain. The stent used in thenew procedure typically is the same stent used for procedures in otherparts of the body, such as the carotid artery. The venous sinusstructure, however, does not resemble any vein or arteries of otherparts of the body. Instead, the venous sinus is a void created where thedura joins and forms a cavity (i.e., sinus) primarily along the insideof the skull. The dura has no smooth muscle cell lining and is inelasticwhen compared to veins and arteries.

FIG. 1 illustrates an exemplary venous sinus system having an identifiedstent zone. The venous sinus system comprises venous channels foundbetween the periosteal and meningeal layers of dura mater in the brain.The venous sinus system receives blood from internal and external veinsof the brain, receives CSF from the subarachnoid space via arachnoidgranulations, and mainly empties into the internal jugular vein. Asillustrated in FIG. 1, the venous sinus system includes the transversesinus, sigmoid sinus, and the sigmoid junction. The sigmoid sinusintegrates into the jugular vein at the sigmoid junction. FIG. 1 alsoidentifies an exemplary stent zone for placing a stent to treat acollapse of and/or a stenosis in the sigmoid and/or transverse sinus.

Existing stent delivery systems and stents have several inadequacies fordelivering a stent to the venous sinuses. For example, existing stentsand systems may be incapable of or difficult to navigate through thetortuous sigmoid junction for placement of the stent in the stent zone.

As another example, the properties of existing stents may be undesirablefor placement in the venous sinuses. The length of a typical carotidartery stent may be 4-6 cm long. However, after placement of a carotidartery stent in the venous sinuses, a portion of the transverse sinuscould collapse, particularly a portion that is distal to the distal endof the stent. The collapse of a portion of the transverse sinus mayoccur if the stent is placed in the sigmoid to transverse junction andis not long enough to scaffold most or the entirety of transverse sinus.Additionally, multiple carotid artery stents may be required if thereare collapses and/or stenosis at multiple locations in the sigmoidand/or transverse sinuses. Also, a stent having an inappropriate lengthcould be incorrectly positioned at the curves in the sigmoid sinus toblock off future access to the sinus (e.g., a stent jail). For example,a stent that terminates within a curve, instead of being positionedthrough the curve, may block a portion or the entire sinus lumen at thecurve.

Furthermore, exiting stents typically come in one set diameter. However,the middle and distal region of the sigmoid sinus has on average alarger diameter (e.g., ˜10-12 mm) than the distal section of thetransverse sinus (e.g., ˜6-9 mm). Accordingly, existing stent diameterspositioned in both the sigmoid and transverse sinuses may be inadequatefor at least one of the sinuses. For example, if the stent is too smallfor a vessel, a portion of the stent can be left dangling or freefloating in the vessel, which may prevent proper endothelium tissuegrowth over the stent struts. As another example, if the stent is toolarge for a vessel, various problems may occur because the radialoutward expansion strength (RES) of typical stents may be too forcefulfor use in the venous sinuses. Specifically, stents intended forplacement in large vessels such as the carotid artery, femoral artery orveins, and the like, may have a high RES required for treatment ofocclusions, atherosclerosis plaque, and lesion calcification, and/orthat can withstand an outside force capable of pushing in on the stent.This high RES, coupled with a stent size that is too large for a vessel,can create a problem of tissue in contact with the stent struts dyingdue to the strong outward pressure exerted on the tissue. Anotherproblem arising with a high RES when stents are too large for a vesselis that the stent may push through the vessel wall and show on theoutside of the vessel.

Existing stent designs may also have an abundance of struts members.However, the venous sinus structure includes numerous small veinsleading from the brain. Accordingly, the quantity of strut members of atypical stent increases the chance that one strut might block, orpartially inhibit the venous inflow from the brain via the veins.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY

Enhanced navigation of a stent delivery system for placement of a stentis provided by increasing the flexibility of the stent delivery systemand/or the stent from the proximal end toward the distal end of thesystem and/or stent, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an exemplary venous sinus system having an identifiedstent zone, in accordance with various embodiments.

FIG. 2 illustrates an exemplary stent comprising a distal end and aproximal end, the distal end having a greater flexibility than theproximal end, in accordance with various embodiments.

FIG. 3 illustrates exemplary strut members of the exemplary stent ofFIG. 2, in accordance with various embodiments.

FIG. 4 illustrates an exemplary profile of the exemplary stent 100 ofFIG. 2 having a distal end with a smaller diameter than the diameter ofthe proximal end, in accordance with various embodiments.

FIG. 5 illustrates an exemplary stent delivery system, in accordancewith various embodiments.

FIG. 6 illustrates a detail view of portions of the exemplary stentdelivery system of FIG. 5, in accordance with various embodiments.

FIG. 7 illustrates a detail view of an inner portion of the stentdelivery system of FIG. 5, in accordance with various embodiments.

FIG. 8 illustrates a detail view of an outer portion of the stentdelivery system of FIG. 5, in accordance with various embodiments.

FIG. 9 illustrates an exploded, cross-sectional view of the innerportion of the stent delivery system, the stent, and the outer portionof the stent delivery system, where the increasing flexibility of thestent delivery system with the stent from the proximal end toward thedistal end of the system and stent is illustrated by a mapping to anexemplary flexibility chart, in accordance with various embodiments.

FIG. 10 is a flow chart illustrating exemplary steps that may beutilized for providing enhanced navigation of a stent delivery systemfor placement of a stent, in accordance with various embodiments.

DETAILED DESCRIPTION

Certain embodiments may provide enhanced navigation of a stent deliverysystem for placement of a stent by increasing the flexibility of thestent delivery system and/or the stent from the proximal end toward thedistal end of the system and/or stent. Various embodiments provide aself-expanding stent that comprises a proximal end having a first radialoutward expansion strength (RES) that is greater than a second RES at adistal end of the stent. In a representative embodiment, the proximalend of the stent comprises a diameter that is greater than the diameterat the distal end of the stent. In certain embodiments, the stentdelivery system may be configured to treat a stenosis or collapse in thevenous sinuses by delivering the self-expanding stent.

The foregoing summary, as well as the following detailed description ofcertain embodiments will be better understood when read in conjunctionwith the appended drawings. It should be understood that the variousembodiments are not limited to the arrangements and instrumentalityshown in the drawings. It should also be understood that the embodimentsmay be combined, or that other embodiments may be utilized and thatstructural changes may be made without departing from the scope of thevarious embodiments. The following detailed description is, therefore,not to be taken in a limiting sense, and the scope of the presentinvention is defined by the appended claims and their equivalents.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features. Moreover, unless explicitlystated to the contrary, embodiments “comprising” or “having” an elementor a plurality of elements having a particular property may includeadditional elements not having that property. As referred to herein, theterms “proximal” and “distal” are in relation to the delivery handle 210of the stent delivery system 200 (also referred to as a catheter). Forexample, the distal end 104, 204 of the stent 100 and the catheter 200is the end that is inserted first into a body lumen of a patient and theproximal end 102, 204 is opposite the distal end 104, 204.

FIG. 2 illustrates an exemplary stent 100 comprising a distal end 104and a proximal end 102, the distal end 104 having a greater flexibilitythan the proximal end 102, in accordance with various embodiments. FIG.3 illustrates exemplary strut members 112 of the exemplary stent 100 ofFIG. 2, in accordance with various embodiments. FIG. 4 illustrates anexemplary profile of the exemplary stent 100 of FIG. 2 having a distalend with a smaller diameter than the diameter of the proximal end, inaccordance with various embodiments. Although FIGS. 2 and 3 mayillustrate the stent 100 in a flat view, the top ends of the stent 100would be joined with the bottom ends to form the stent 100 in acylindrical form. Referring to FIGS. 2-4, the self-expanding cylindricalstent 100 comprises a distal end 104, a proximal end 102, and aplurality of circumferential strut segments 110. The strut segments 110may comprise strut members 112 and longitudinal connecting members 118.The strut members 112 may be arranged in a pattern, such as a zig-zagpattern having peaks 114 and valleys 116, or any suitable pattern. Thestrut segments 110 may each be coupled to at least one other strutsegment 110 by the longitudinal connecting members 118.

Stents are typically implemented as either an open cell stent or aclosed cell stent. A closed cell stent has each peak and valley of eachstrut segment connected to a peak or valley of an adjacent strutsegment, with the exception of the strut segments on the proximal anddistal ends. Open cell stents, on the other hand, have some peaks and/orvalleys that are not connected to peaks and/or valleys of adjacent strutsegments. In a preferred embodiment, the stent 100 may be an open celldesign, for example, to minimize the reduction in length of the stent100 when expanding the stent 100 from a pre-deployed state to a deployedstate. Moreover, an open cell stent structure has an enhanced ability toexpand and conform to a non-circular cavity wall, such as the sinuses,than a closed cell structure. For example, the individual segments of anopen cell stent have less dependence on neighbor segments than in aclosed cell design. Accordingly, the open cell segments are bettersuited for conforming to irregularities of a non-circular cavity.Referring to FIG. 3, the longitudinal connecting members 118 may bearranged in a periodic peak-to-valley connection scheme, such as everythird peak connected to every third valley by a longitudinal connectingmember 118. Although a peak-to-valley connection scheme with a period ofthree is illustrated in FIG. 3, other connection schemes and periods arecontemplated. For example, the connections scheme may be a peak-to-peakconnection scheme, midstrut-to-midstrut connection scheme, a hybridconnection scheme, or any suitable connection scheme. As anotherexample, the period may be two, four, variable periods, or the like.Furthermore, the longitudinal connecting member 118 may be flexconnections, non-flex connections, a hybrid of flex and non-flexconnections, or any suitable connections.

The stent 100 may be sized to cover the sigmoid sinus and substantiallythe entire transverse sinus. For example, depending on a size and heightof a patient, the length of the stent may be 6-9 cm long with a mean ofapproximately 7 cm. The appropriately sized stent maintains patency ofboth sinus structures while substantially eliminating the chance of are-collapse and substantially eliminating the possibility of a stentjail.

The stent 100 may be made of nickel titanium, also known as nitinol, orany suitable material. In the case of a nitinol stent 100, the collapsedstent 100 can be inserted into a body lumen, where body temperaturewarms the stent 100 and the stent 100 returns to its original expandedshape following removal of a constraining sheath as described below withreference to FIGS. 5-10.

In various embodiments, the stent 100 may comprise segments 110 of strutmembers 112 having different flexibility. Specifically, one or moresegments 110 at the distal end 104 of the stent 100 may have a greaterflexibility than one or more segments 110 at the proximal end 102 of thestent 100. For example, as illustrated in FIG. 2, the stent 100 may havea first group of flexible segments 120 and a second group of stiffsegments 130. The first group of flexible segments 120 may include eightor any suitable number of segments 110 and the second group of stiffsegments 130 may include fourteen or any suitable number of segments110. The stent 100 may transition from the group of flexible segments120 to the group of stiff segments 130 at a transition point 142 betweenthe two groups 120, 130. FIG. 3 illustrates the detail of the transition142 between the flexible segments 120 and stiff segments 130.Additionally and/or alternatively, the segments 110 of the stent 100 mayprogressively increase in stiffness from the distal end 104 to theproximal end 102 of the stent 100. For example, each segment 110 mayhave the same or more flexibility than the adjacent segment 110 in theproximal end 102 direction.

In a representative embodiment, the flexibility of a segment 110 maycorrespond with the radial outward expansion strength (RES) of thatsegment 110. For example, the group of flexible segments 120 may have alower RES than the group of stiff segments 130. Accordingly, if placingthe stent in the venous sinuses, the group of flexible segments 120having the low RES at the distal end 104 of the stent 100 may scaffoldand hold open the transverse sinus region while not exerting too muchpressure to the dura inner lining. The group of stiff segments 130 atthe proximal end of the stent 100 and having an RES greater than theflexible segments 120 are positioned in the sigmoid region that cancontain excessive arachnoid granulation ingrowth and/or stenosis thatmay require more force to open and restore better blood outflow. The lowRES distal end 104 of the stent 100 transitioning to a higher RESproximal end 102 may translate to a more flexible and integraltransition within the stent delivery system 200. Specifically, theintegration of the stent 100 in the stent delivery system 200 provides afaster and easier delivery of the stent 100 by improving the ability tonavigate the sigmoid junction, as described below with reference to FIG.9, for example.

In various embodiments, the amount of RES and flexibility of portions ofthe stent 100 may be constructed based on the distance between stentsegments 110 and/or the length of the longitudinal connecting members118, the number of longitudinal connecting members 118, the amount ofstrut members 112, and/or the width of the strut members 112 and/or thelongitudinal connecting members 118. For example, a greater distancebetween stent segments 110 and/or longer longitudinal connecting member118 may correspond with a lower RES and greater flexibility. As anotherexample, a larger number of longitudinal connecting members 118 maycorrespond with a higher RES and greater stiffness. Furthermore, agreater amount of strut members 112 may correspond with a higher RES andlarger stiffness. Additionally, a narrower width of the strut members112 and/or the longitudinal connecting members 118 may correspond with alower RES and greater flexibility. For example, referring to FIG. 3, thewidths of the strut members 112, strut member peaks 114, andlongitudinal members 118 in the group of stiff segments 130 are referredto as W1. The widths of the strut members 112, strut member peaks 114,and longitudinal members 118 in the group of flexible segments 120 arereferred to as W2. The widths W1 in the group of stiff segments 130 maybe greater than the widths W2 in the group of flexible segments 120. Asan example, the width W1 of the strut members 112 and longitudinalmembers 118 in the group of stiff segments 130 may be approximately0.0050 inches and the width W1 of the strut member peaks 114 may beapproximately 0.0065 inches. In the group of flexible segments 120, thewidth W2 of the strut members 112 and the longitudinal connectingmembers 118 may be approximately 0.0045 inches and the width W2 of thestrut member peaks 114 may be approximately 0.0060 inches. In certainembodiments, the approximately 10 percent reduction in width W2 maycorrespond with a reduction in stiffness by approximately 33 percent ofthe group of flexible segments 120 compared to the group of stiffsegments 130.

Referring to FIG. 4, the stent 100 may be conically shaped or steppedsuch that the lumen diameter D1/D2 of the stent 100 is greater at theproximal end 102 than at the distal end 104. FIG. 4, for example,illustrates a profile of a cylindrical stent 100 that is conicallyshaped and includes a greater lumen diameter D1 of the stent 100 at theproximal end 102 than the stent lumen diameter D2 at the distal end 104.Additionally and/or alternatively, the stent 100 may have a mix ofstraight and conical portions. For example, the stent 100 may havestraight portions at the distal 104 and proximal 102 ends with a conicalportion therebetween. As another example, the stent 100 may have astraight portion at the distal end 104 followed by a conical portionbetween the straight portion and the proximal end 102, or vice versa.The inclusion of a conical portion ensures different lumen diametersD1/D2 at the proximal 102 and distal 104 ends of the stent 100. In arepresentative embodiment, the proximal end 102 of the stent 100 has agreater diameter D1 than the diameter D2 at the distal end 104. Forexample, the diameter D1 at the proximal end 102 may be approximately0.3937 inches and the diameter D2 at the distal end 104 may beapproximately 0.2756 inches. Accordingly, if placing the stent 100 inthe venous sinuses, the smaller diameter D2 at the distal end 104 of thestent may be appropriately sized for the transverse sinus region and thetransition to the larger diameter D1 at the proximal end 102 of thestent 100 may be appropriately sized for the sigmoid sinus region. Inthat way, the contact between the strut members 112 and the dura wall ofboth the transverse sinus region and the sigmoid sinus region may bemaximized so that portions of the stent 100 are not left free in theopen blood flow of the lumen of the venous sinuses.

FIG. 5 illustrates an exemplary stent delivery system 200, in accordancewith various embodiments. FIG. 6 illustrates a detail view of portions200A, 200B, 200C, 200D of the exemplary stent delivery system 200 ofFIG. 5, in accordance with various embodiments. FIG. 7 illustrates adetail view of an inner portion 200E of the stent delivery system 200 ofFIG. 5, in accordance with various embodiments. FIG. 8 illustrates adetail view of an outer portion 200F of the stent delivery system 200 ofFIG. 5, in accordance with various embodiments. FIG. 9 illustrates anexploded, cross-sectional view of the inner portion 200E of the stentdelivery system 200, the stent 100, and the outer portion 200F of thestent delivery system 200, where the increasing flexibility of the stentdelivery system 200 with the stent 100 from the proximal end 102, 202toward the distal end 104, 204 of the system 200 and stent 100 isillustrated by a mapping to an exemplary flexibility chart 300, inaccordance with various embodiments.

Referring to FIGS. 5-9, a stent delivery system 200 may comprise anouter portion 200F and an inner portion 200E extending between aproximal end 202 and a distal end 204 of the system 200.

The inner portion 200E of the stent delivery system 200 may comprise adelivery handle 210 at the proximal end 202, a delivery tip 290 at thedistal end 204, and a shaft 220 extending from the delivery handle intothe delivery tip 290. The shaft 220 may comprise a proximal portion ofthe shaft 222 that connects to the delivery handle 210, a centralportion of the shaft 224, and a distal portion of the shaft 226 thatincludes and/or extends through a push coil 270 and a stent bed 280. Invarious embodiments, the shaft portions 222, 224, 226, 270, 280 may betubular structures that are made of different materials and/or may havedifferent outer diameters, for example, to increase flexibility from theproximal end 202 along a longitudinal axis to the distal end 204. Forexample, the proximal portion of the shaft 222 attached to the deliveryhandle and the central portion of the shaft 224 may be a hypotube or anysuitable tube having a first diameter. The distal portion of the shaft224 may have a second diameter that is less than the first diameter ofthe proximal 222 and central 224 portions and/or may include sectionsmade of different materials such as a coiled section 270.

The stent bed 280 may be the portion of the distal shaft 226 between thepush coil 270 and the delivery tip 290. The stent bed 280 may be a thinwall polyimide tube having a constant stiffness. The stent bed 280 mayextend through a lumen in a pre-deployed stent 100 such that thepre-deployed stent 100 is positioned and carried on the stent bed 280until deployment. The pre-deployed stent 100 positioned on the stent bed280 may be held in a pre-deployed state by sheathing 260 that isslidable over the stent 100 as described below. In various embodiments,the proximal and/or distal ends of the stent bed 280 may include one ormore markers, such as radio-opaque markers, to enhance visualization ofthe location of the pre-deployed stent 100 within the stent deliverysystem 200. For example, an operator of the stent delivery system 200may monitor the navigation of the system 200 via medical image data,such as fluoroscopic images, ultrasound images, or images of anysuitable medical imaging modality. The marker(s) may be readilyidentifiable in the image data to assist the operator in accuratelypositioning the stent delivery system 200 in the stent zone.

The push coil 270 may be a portion of the distal shaft 226 at a proximalend of the stent bed 280. Additionally and/or alternatively, the pushcoil 270 may be arranged concentrically between the distal shaft 226 andthe sheathing 260. The push coil 270 may act as a stop for a stent 100positioned on the stent bed 280 by preventing the pre-deployed stent 100from sliding from the stent bed 280 toward the proximal end 202. Invarious embodiments, the push coil 270 may have a greater flexibility ata distal end of the coil 270 than at the proximal end of the coil 270.For example, the push coil 270 may have a plurality of sections, whereeach of the sections has an increased flexibility from the proximal endof the coil 270 along a longitudinal axis to the distal end of the coil270.

The delivery tip 290 may comprise a distal end 294 and a proximal end292. The delivery tip 290 may comprise a lumen configured to allow aguidewire 269 to pass through the delivery tip 290 such that the stentdelivery system may glide over the guidewire 290 during navigation ofthe system to the stent zone in the venous sinuses or other body lumen.The delivery tip 290 may comprise a tip transition 296 at the proximalend 292 of the delivery tip 290. The tip transition 296 may have alarger outer diameter configured to prevent the sheathing 260 of theouter portion 200F of the stent delivery system 200 from slidingdistally over the delivery tip 290. In a representative embodiment, thedelivery tip 290 may be made of a medical grade polymer, e.g., polyetherblock amide, such as PEBAX, and may have a durometer of approximately35.

In various embodiments, the stent delivery system 200 may include arapid exchange junction 268 through the sheathing 260 and into thedistal shaft portion 226. The guidewire 269 runs within a guidewirelumen in the stent delivery system 200 from the lumen in the deliverytip 290 at the distal end 204 of the system 200 to a point where theguidewire lumen terminates on the outside of the system 200 at the rapidexchange junction 268 at the distal shaft portion 226 and distalsheathing portion 266 that is proximal the push coil 270. The rapidexchange junction 268 may facilitate the rapid placement of the stentdelivery system 200 over the guidewire 269 and allow for the use ofshorter guidewires than used in over-the-wire catheter systems.

The outer portion 200F of the stent delivery system 200 may comprise ahub 230, 240, 250 and sheathing 260. The hub may comprise a lock 230, aTuohy Borst valve 240, and a Luer wing 250. The lock 230 may be, forexample, a standard Luer lock or any suitable lock for connecting theTuohy Borst valve 240 to the proximal portion 222 of the shaft 220. Thelock 230 may be loosened to allow the hub 230, 240, 250 and sheathing260 to slide over the shaft 220 and may be tightened to prevent suchmovement. The Tuohy Borst valve (also known as a hemostasis valve) 240may be attached to the lock 230 at a proximal end and may be coupled toa Luer wing 250 at a distal end. The Tuohy Borst valve 240 may receivethe internally inserted shaft 220 that can move within the valve 240 ina direction parallel to its longitudinal axis. The Tuohy Borst valve 240may include a Luer port 242 for securing the valve 240 to other medicalinstruments and devices that may be used during a procedure to deliver astent 100 to the stent zone within a patient. The Luer wing 250 maysecurely attach to the sheathing 260. The shaft 220 is configured toextend through the lock 230, Tuohy Borst valve 240, Luer wing 250, andsheathing 260.

The sheathing 260 may include a proximal portion 262 terminating at theLuer wing 250, a distal portion 266 terminating at the tip transition296 at the proximal end 292 of the delivery tip 290, and a centralportion 264 between the proximal 262 and distal 266 portions. In variousembodiments, the sheathing portions 262, 264, 266 may be tubularstructures that are made of different materials and/or may havedifferent outer diameters, for example, to increase flexibility from theproximal end 202 along a longitudinal axis to the distal end 204. Thesheathing 260 is configured to slide longitudinally over the shaft 220and stent 100 between a pre-deployed position and a deployed position.For example, in a pre-deployed position, the sheathing 260 extends overthe pre-deployed stent 100 to the tip transition 296 of the delivery tip290. After the stent delivery system 200 is navigated to the stent zone,the sheathing 260 may be pulled back over the stent 100 by releasinglock 230 and pulling the hub 230, 240, 250 toward the delivery handle210 at the proximal end 202 of the system 200. The stent 100 deploys byexpanding as the sheathing 260 passes over and releases the stent 100from its pre-deployed compressed state. In various embodiments, thesheathing 260 may comprise one or more markers, such as radio-opaquemarkers, to enhance visualization in medical image data of the locationof the pre-deployed stent 100 within the stent delivery system 200. In arepresentative embodiment, the distal portion 266 of the sheathing 260may be made of a medical grade polymer, e.g., polyether block amide,such as PEBAX. In an exemplary embodiment, the distal portion 266 of thesheathing 260 may include a most distal section 266 a having a flexibledurometer of approximately 35, a central section 266 b having asemi-flexible durometer of approximately 55, and a proximal section 266c having a stiff durometer of approximately 72. In this way, thestiffness of the distal portion 266 of the sheathing 260 may increasefrom the most distal section 266 a to the proximal section 266 c.

Referring to FIG. 9, a chart 300 is shown mapping the stiffness orflexibility 302 of the combined inner portion 200E of the stent deliverysystem 200, stent 100, and outer portion 200F of the stent deliverysystem 200. As shown in FIG. 9, the stiffness 302 gradually increasesand/or steps up from the distal end 204 of the stent delivery system 200having the loaded stent 100 toward the proximal end 202 of the system200. For example, the delivery tip may have a durometer of approximately35. As shown in FIG. 9, the delivery tip 290 portion of the stentdelivery system 200 may be the most flexible 302. The next section inthe proximal direction from the delivery tip 290 is the stent bed 280loaded with the stent 100 and a section of the distal portion of thesheathing 266. The distal portion 266 of the sheathing 260 may have amost distal section 266 a having a flexible durometer of approximately35. Accordingly, the combination of the distal portion 266 of thesheathing with the stent bed 280 and the flexible group of segments 120of the stent 100 may have a greater stiffness 302 than the delivery tip290. Continuing in the proximal direction, the stiffness 302 of thecombination of the most distal section 266 a of the distal portion ofthe sheathing 266, the stiff group of segments 130 of the stent 100, andthe stent bed 280 increases due to the stiffer group of segments 130 ofthe stent 100.

The central section 266 b of the distal portion 266 of the sheathing mayhave a semi-flexible durometer of approximately 55 and the proximalsection 266 c may have a stiff durometer of approximately 72. The pushcoil 270 may have a flexible section 272 with loose windings and a stiffsection 274 having tight windings. Consequently, the stiffness 302continues to increase for the combination of the flexible section 272 ofthe coil 270 and the central section 266 b of the distal portion of thesheathing 266. In the same way, the stiffness 302 steps up for thecombination of the stiff section 274 of the coil and the central section266 b of the distal portion of the sheathing 266.

The distal shaft portion 226 in the proximal direction from the coil 270may have a greater stiffness than the coil. Accordingly, the stiffness302 of the stent delivery system 200 having the loaded stent 100 maystep up again for the combined system components including the distalshaft portion 226 in the proximal direction from the coil 270 and theproximal section 266 c of the distal portion 266 of the sheathing 260.

In summary, not only does the different materials and the differentdurometer of the individual components effect the flexibility of thestent delivery system 200 having the loaded stent 100, but thecombination of components along the longitudinal axis of the system 200loaded with the stent 100 provides a gradual increase in of stiffness302 from the distal end 204 toward the proximal end 202 of the system200 in a new way that improves control and navigation of the system 200for delivering the stent 100.

FIG. 10 is a flow chart 400 illustrating exemplary steps 402-410 thatmay be utilized for providing enhanced navigation of a stent deliverysystem 200 for placement of a stent 100, in accordance with variousembodiments. Referring to FIG. 10, there is shown a flow chart 400comprising exemplary steps 402 through 410. Certain embodiments may omitone or more of the steps, and/or perform the steps in a different orderthan the order listed, and/or combine certain of the steps discussedbelow. For example, some steps may not be performed in certainembodiments. As a further example, certain steps may be performed in adifferent temporal order, including simultaneously, than listed below.

At step 402, a stent delivery system 200 may be inserted into the venoussinuses or other body lumen. For example, the stent delivery system 200may access the venous sinuses at the sigmoid junction via the jugularvein. The stent delivery system 200 may include a collapsed,pre-deployed stent 100 carried between a shaft 220 and/or stent bed 280and sheathing 260 near the distal end 203 of the system 200. In variousembodiments, the stent 100 may be made of nitinol. The insertion of thestent delivery system 200 into the venous sinuses or other body lumenprovides body temperature that warms the nitinol stent 100, which allowsthe stent 100 to return to its original expanded shape after a sheath260 of the system is removed at step 408.

At step 404, the stent delivery system 200 is navigated to position thestent 100 at a target site in the venous sinuses or other body lumen.For example, the stent delivery system 200 may access the venous sinusesvia the jugular vein, through the sigmoid junction and sigmoid sinus,and into transverse sinus. The target site, or stent zone, for placementof the stent 100 may span from substantially the distal end of thetransverse sinus into the sigmoid sinus. The navigation of the stentdelivery system 200 having the stent 100 includes traversing thetortuous sigmoid junction. Accordingly, in various embodiments, both thestent 100 and the stent delivery system 200 may have a flexibility thatincreases from the proximal end 102, 202 of the stent 100 and catheter200 to the distal end 104, 204 of the stent 100 and catheter 200. Thisprogressive change in flexibility provides increased maneuverability atthe distal end 104, 204 while providing the stiffness to control thesystem 200 toward the proximal end 102 of the system 200.

At step 406, the lock 230 of the stent delivery system 200 is releasedto allow movement of the sheathing 260 over the shaft 220 of the system200. For example, lock 230 may be unscrewed or otherwise loosened fromthe shaft 220.

At step 408, the catheter hub 230, 240, 250 may be pulled toward thedelivery handle 210 to slide the sheathing 260 back over the stent 100to deploy the stent 100. For example, the sheathing may be attached tothe catheter hub 230, 240, 250 at the Luer wing 250 such that when thehub 230, 240, 250 is pulled over the shaft 220, the sheathing 260 moveswith the hub 230, 240, 250.

At step 410, the delivery tip 290 may be pulled through the lumen in thedeployed stent 100 and the stent delivery system 200 may be removed fromthe venous sinuses or other body lumen. For example, the removal of thesheathing 260 at step 408 may deploy the collapsed stent 100 to anexpanded state that opens the stent lumen. Accordingly, the delivery tip290 of the stent delivery system 200 may pass through the opened stentlumen as the stent delivery system 200 is pulled back through and out ofthe venous sinuses or other body lumen to remove the stent deliverysystem 200 from the patient.

Aspects of the present invention provide a stent delivery system 200. Inaccordance with various embodiments, the stent delivery system 200comprises a delivery handle 210 at a proximal end 202 of the stentdelivery system 200, a catheter hub 230, 240, 250, a delivery tip 290 ata distal end 204 of the stent delivery system 200, a shaft 220, a stent100, and sheathing 260. The delivery tip 290 comprises a tip distal end294 and a tip proximal end 292. The delivery tip 290 has a firstflexibility. The shaft 220 extends from the delivery handle 210 throughthe catheter hub 230, 240, 250 and into the delivery tip 290. The shaft220 comprises a coil 270 and a stent bed 280. The coil 270 comprises acoil distal end and a coil proximal end. The stent bed 280 is betweenthe coil distal end and the tip proximal end 292. The stent 100 isloaded on to the stent bed 280 and comprises a stent distal end 104, astent proximal end 102, and a cylindrical body between the stent distalend 104 and the stent proximal end 102. A first portion 120 of thecylindrical body at the stent distal end 104 has a greater flexibilitythan a second portion 130 of the cylindrical body at the stent proximalend 130. The sheathing 260 is coupled to the catheter hub 230, 240, 250and moveable over the stent bed 280 between pre-deployed and deployedpositions. The sheathing 260 extends over the stent bed 280 if in thepre-deployed position. The sheathing 260 is pulled back from the stentbed 280 if in the deployed position. The stent 100 is compressed by thesheathing 260 on the stent bed 280 if in the pre-deployed position. Thestent 100 expands if the sheathing 260 is pulled back from the stent bed280 in the deployed position. The sheathing 260 comprises a sheathingdistal end and a sheathing proximal end. The sheathing 260 comprises aflexible section 266 a at the sheathing distal end, a semi-flexiblesection 266 b adjacent the flexible section 266 a, and a stiff section266 c adjacent the semi-flexible section 266 b. The combination of thestent bed 280, the first portion 120 of the cylindrical body of thestent 100, and the flexible section 266 a of the sheathing 260 has asecond flexibility that is less than the first flexibility. Thecombination of the stent bed 280, the second portion 130 of thecylindrical body of the stent 100, and the flexible section 266 a of thesheathing 260 has a third flexibility that is less than the secondflexibility.

In various embodiments, the coil 270 comprises a loose wound region 272at the coil distal end having a greater flexibility than a tight woundregion 274 of the coil 270 at the coil proximal end. In certainembodiments, the combination of the loose wound region 272 of the coil270 and the semi-flexible section 266 a of the sheathing 260 has afourth flexibility that is less than the third flexibility. In arepresentative embodiment, the combination of the tight wound region 274of the coil 270 and the semi-flexible section 266 b of the sheathing 260has a fifth flexibility that is less than the fourth flexibility. Invarious embodiments, the combination of the tight wound region 274 ofthe coil 270 and the stiff section 266 c of the sheathing 260 has asixth flexibility that is less than the fifth flexibility. In certainembodiments, the shaft 220 adjacent the coil 270 at the coil proximalend in combination with the stiff section 266 c of the sheathing 260 hasa seventh flexibility that is less than the sixth flexibility.

In a representative embodiment, one or more of the delivery tip 290 andthe sheathing 260 is made of a medical grade polymer, e.g., polyetherblock amide. In various embodiments, the stent bed 280 is a thin walltube having a constant stiffness. In certain embodiments, the deliverytip 290 has a durometer of approximately 35. In a representativeembodiment, one or more of the flexible section 266 a of the sheathing260 has a durometer of approximately 35, the semi-flexible section 266 bof the sheathing 260 has a durometer of approximately 55, and the stiffsection 266 c of the sheathing 260 has a durometer of approximately 72.

Various embodiments provide a stent 100 comprising a distal end 104having a first diameter D2, a proximal end 102 having a second diameterD1 that is greater than the first diameter D2, and a cylindrical bodybetween the distal end 104 and the proximal end 102. The cylindricalbody comprises circumferential strut segments 110 and longitudinalconnecting members 118. Each of the circumferential strut segments 110comprises strut members 112 arranged in a pattern. Each of thecircumferential strut segments 110 is connected to at least one other ofthe circumferential strut segments 110 by a portion of the longitudinalconnecting members 118. A first plurality of the circumferential strutsegments 120 at the distal end 104 of the stent 100 has a greaterflexibility than a second plurality of the circumferential strutsegments 130 at the proximal end 102 of the stent 100.

In certain embodiments, the first plurality of the circumferential strutsegments 120 at the distal end 104 of the stent 100 has a lower radialoutward expansion strength than the second plurality of thecircumferential strut segments 130 at the proximal end 102 of the stent100. In a representative embodiment, at least a portion of thecylindrical body is conically-shaped. In various embodiments, thelongitudinal connecting members 118 are arranged as an open cell design.In certain embodiments, the cylindrical body is made of nickel titanium.In a representative embodiment, the cylindrical body is 6 to 9centimeters long.

In various embodiments, the pattern of the strut members 112 is a zigzag pattern having peaks 114 and valleys 116. In certain embodiments,the longitudinal connecting members 118 are arranged in a periodicpeak-to-valley connection scheme. In a representative embodiment, afirst width W2 of one or both of the strut members 112 and thelongitudinal connecting members 118 of the first plurality of thecircumferential strut segments 120 at the distal end 104 of the stent100 is less than a second width W1 of one or both of the strut members112 and the longitudinal connecting members 118 of the second pluralityof the circumferential strut segments 130 at the proximal end 102 of thestent 100. In various embodiments, the first plurality of thecircumferential strut segments 120 at the distal end 104 of the stent100 is 8 circumferential strut segments 110 and the second plurality ofthe circumferential strut segments 130 at the proximal end 102 of thestent 100 is 14 circumferential strut segments 110.

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. As an example, “x and/or y” means any elementof the three-element set {(x), (y), (x, y)}. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. As utilized herein, the term “exemplary”means serving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, a structure that is “configured” to or “operable” toperform a function requires that the structure is more than just capableof performing the function, but is actually made to perform thefunction, regardless of whether the function is actually performed.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A stent delivery system, comprising: a deliveryhandle at a proximal end of the stent delivery system; a catheter hub; adelivery tip at a distal end of the stent delivery system, wherein thedelivery tip comprises a tip distal end and a tip proximal end, andwherein the delivery tip has a first flexibility; a shaft extending fromthe delivery handle through the catheter hub and into the delivery tip,wherein the shaft comprises a coil and a stent bed, the coil having acoil distal end and a coil proximal end, the stent bed between the coildistal end and the tip proximal end; a stent loaded on to the stent bed,wherein the stent comprises a stent distal end, a stent proximal end,and a cylindrical body between the stent distal end and the stentproximal end, and wherein a first portion of the cylindrical body at thestent distal end has a greater flexibility than a second portion of thecylindrical body at the stent proximal end; and sheathing coupled to thecatheter hub and moveable over the stent bed between pre-deployed anddeployed positions, wherein the sheathing extends over the stent bed ifin the pre-deployed position, wherein the sheathing is pulled back fromthe stent bed if in the deployed position, wherein the stent iscompressed by the sheathing on the stent bed if in the pre-deployedposition, wherein the stent expands if the sheathing is pulled back fromthe stent bed in the deployed position, wherein the sheathing comprisesa sheathing distal end and a sheathing proximal end, and wherein thesheathing comprises a flexible section at the sheathing distal end, asemi-flexible section adjacent the flexible section, and a stiff sectionadjacent the semi-flexible section, wherein the combination of the stentbed, the first portion of the cylindrical body of the stent, and theflexible section of the sheathing has a second flexibility that is lessthan the first flexibility, and wherein the combination of the stentbed, the second portion of the cylindrical body of the stent, and theflexible section of the sheathing has a third flexibility that is lessthan the second flexibility.
 2. The system according to claim 1, whereinthe coil comprises a loose wound region at the coil distal end having agreater flexibility than a tight wound region of the coil at the coilproximal end.
 3. The system according to claim 2, wherein thecombination of the loose wound region of the coil and the semi-flexiblesection of the sheathing has a fourth flexibility that is less than thethird flexibility.
 4. The system according to claim 3, wherein thecombination of the tight wound region of the coil and the semi-flexiblesection of the sheathing has a fifth flexibility that is less than thefourth flexibility.
 5. The system according to claim 4, wherein thecombination of the tight wound region of the coil and the stiff sectionof the sheathing has a sixth flexibility that is less than the fifthflexibility.
 6. The system according to claim 5, wherein the shaftadjacent the coil at the coil proximal end in combination with the stiffsection of the sheathing has a seventh flexibility that is less than thesixth flexibility.
 7. The system according to claim 1, wherein one ormore of the delivery tip and the sheathing is made of a medical gradepolymer.
 8. The system according to claim 1, wherein the stent bed is athin wall tube having a constant stiffness.
 9. The system according toclaim 1, wherein the delivery tip has a durometer of approximately 35.10. The system according to claim 1, wherein one or more of: theflexible section of the sheathing has a durometer of approximately 35,the semi-flexible section of the sheathing has a durometer ofapproximately 55, and the stiff section of the sheathing has a durometerof approximately
 72. 11. A stent, comprising: a distal end having afirst diameter; a proximal end having a second diameter that is greaterthan the first diameter; and a cylindrical body between the distal endand the proximal end, the cylindrical body comprising circumferentialstrut segments and longitudinal connecting members, each of thecircumferential strut segments comprising strut members arranged in apattern, and each of the circumferential strut segments connected to atleast one other of the circumferential strut segments by a portion ofthe longitudinal connecting members, wherein a first plurality of thecircumferential strut segments at the distal end of the stent has agreater flexibility than a second plurality of the circumferential strutsegments at the proximal end of the stent.
 12. The stent according toclaim 11, wherein the first plurality of the circumferential strutsegments at the distal end of the stent has a lower radial outwardexpansion strength than the second plurality of the circumferentialstrut segments at the proximal end of the stent.
 13. The stent accordingto claim 11, wherein at least a portion of the cylindrical body isconically-shaped.
 14. The stent according to claim 11, wherein thelongitudinal connecting members are arranged as an open cell design. 15.The stent according to claim 11, wherein the cylindrical body is made ofnickel titanium.
 16. The stent according to claim 11, wherein thecylindrical body is 6 to 9 centimeters long.
 17. The stent according toclaim 11, wherein the pattern of the strut members is a zig zag patternhaving peaks and valleys.
 18. The stent according to claim 17, whereinthe longitudinal connecting members are arranged in a periodicpeak-to-valley connection scheme.
 19. The stent according to claim 11,wherein a first width of one or both of the strut members and thelongitudinal connecting members of the first plurality of thecircumferential strut segments at the distal end of the stent is lessthan a second width of one or both of the strut members and thelongitudinal connecting members of the second plurality of thecircumferential strut segments at the proximal end of the stent.
 20. Thestent according to claim 11, wherein the first plurality of thecircumferential strut segments at the distal end of the stent is 8circumferential strut segments and the second plurality of thecircumferential strut segments at the proximal end of the stent is 14circumferential strut segments.